Use standard F# suffix notation for relevant generics

[cmeeren]

In many functions, e.g., Option.traverseAsync, the parameters and/or return types are typed as Option<'T>. The official F# guidelines specify to use 'T option (suffix notation) for certain types. This could also apply to other types or [] vs. array (see the link for details).

This is relevant for consumers of this library, and not just for the library itself, because the type annotations used in the library propagate into user code.

(Unfortunately I have no capacity to contribute a PR for this.)